If I were in a Ska band, I would want something with a fast neck, so something like an American Jazz bass, or an Ernie Ball Sterling. This is all my opinion, but you should just try as many as you can, then pick. I don't think you could go wrong with either of my suggestions though.

I have mixed feelings on this, as a builder, I have always felt that it's a great thing when players find an instrument that works for them and best displays who they are, in tone, appearance and feel. Every player is an individual, and every player, no matter what their style, no matter what their experience level, will have their own voice, and their instrument should reflect that.
However, as a player, I have often used a different instrument on different projects to get a certain sound. Also, I have seen enough evidence in my own playing and in my students to know that every player will have their own voice regardless of the instrument. I guess for me it depends on the project. When I go out and play in my own group, I use my "signature" instrument and sound, but if I'm recording for someone else or want a specific tone on a project, I'll use whatever gets the job done best. Oh well.